By Michael O'Hare

One of California’s great strengths is the repertoire of ideas and practices that our diverse immigrant population brings from all over. However, some really good ideas from elsewhere have trouble taking root here and, as an East Coast import, I have been especially puzzled that owner-occupied rental housing, a pattern that has worked so well there, is an object of suspicion and even hostility in California.

I know of no neighborhood pattern that does so many useful things around the city as owner-occupied rental housing. San Francisco took a couple of tentative steps in the right direction last year, and on March 24 the Berkeley City Council will consider new rules for “accessory dwelling units” (or mother-in-law apartments), so perhaps the practice will thrive and spread. It should.

When you rent out a small unit in your house, or a cottage in your backyard, a number of nice things happen. You have someone to feed the cat when you go skiing, or turn off the stove when you forget and go out, and there’s an eye on your home most of the time. The tenants are not going to be jerks or abusive, and neither are you going to leave a broken toilet unattended or gouge them on the rent. Empty nesters, trapped in too much house by Proposition 13 tax rules, can afford to stay in it many more years, maybe even renting the unit to a caregiver when they need some help. Or your yo-yo kids can have a landing spot, and you can hang with the grandchildren without having them completely underfoot. If you’re a young professional couple starting out, you can afford a bigger house (just take over the rental unit for a couple of decades) when you have kids without having to move; as tenants, you can start out in a neighborhood you can stay in when you need more space.

The most important benefits of owner-occupied rental housing, however, are broader than the owners’ and tenants’ convenience. Obviously, one is simply providing more, and more affordable, housing and increasing density, with all the advantages (walkable neighborhoods, better transit, less climate-changing greenhouse-gas emissions) it brings. Neighborhoods of this type are stable because they have a mix of ages and incomes. There is less turnover because the housing can adapt to owners’ changing needs while they stay put.

My parents bought a New York brownstone row house in 1946 and rented out the bottom two floors, so I grew up in a house and neighborhood we couldn’t have afforded otherwise. We got to know an interesting sequence of tenants, including Lena Horne and the premier architectural photographer of the time. In Boston, the corresponding housing type is 10-room Victorians originally built for families with servants, cut up into a large unit and one or two small ones. There are also, famously, the “three-deckers,” flat-roofed, three-unit, walk-ups with a small yard, separated by a driveway. They were originally built by the tens of thousands as rental apartments for blue-collar workers, and as tenants bought, adapted and remodeled them, they have served well for more than a century. I was a tenant in a three-decker and, later, when we bought a big old Brookline Victorian, we had an apartment on the third floor for my aging mother, and another over a separate garage: That one housed an au pair couple while our kids were young, and graduate students later on. Almost all my friends lived in variations of these arrangements, and we thought it completely natural and practical.

The Bay Area is suffocating from a really desperate shortage of middle-class housing and the wasteful commuter-traffic nightmare such a shortage generates — mother-in-law units would address all of this. High housing prices are nice (for a while) for those lucky enough to already own, but it’s really toxic when teachers, firefighters and the guys who fix the streets can’t live anywhere near where they work. Most of these middle-income workers are forced to find housing in the far-flung suburbs, and suffer hour-plus-long commutes. Anyone in New York or Boston — prosperous cities with very healthy property values — would see resistance to owner-occupied rental housing as one more inexplicable California eccentricity, like our prickly attitude toward public transit.

Maybe my Bay Area neighbors are afraid — What will renters do to housing values? — in the same way my Southern California undergraduate students are afraid to go East for graduate school: never having experienced a New England winter in boots and a down parka, they subconsciously imagine themselves navigating Harvard Square in January in a tank top and flip-flops. This chills any idea of seeking an educational experience that might serve them well.

Try it, neighbors: There are already more and more illegal accessory dwelling units slipping under the radar of building codes and stiffing our community of property tax and income tax on rental income. The market is trying to tell us something: Owner-occupied rental housing deserves to come out in the California sunshine.

Michael O’Hare, an architect and engineer by training, is professor of public policy at UC Berkeley’s Goldman School of Public Policy. This article was originally posted in the San Francisco Chronicle.